Project Description Acute myocardial infarction (AMI) is a major cause of morbidity and mortality worldwide. Nearly 200,000 patients die yearly of AMI in the US alone. AMI is caused by a sudden thrombotic obstruction to the flow in a coronary artery branch leading to myocardial ischemia (lack of oxygen) and tissue death. The most common long-term complication of AMI is the late occurrence of left ventricular dysfunction and heart failure. Limiting the extension of myocardial damage and thus preventing late occurrence of heart failure remains a current clinical challenge. Our recent innovative studies have demonstrated that potent phosphodiesterase-5 (PDE-5A) inhibitors including sildenafil citrate (Viagra) and vardenafil (Levitra) induce powerful cardioprotective effect against ischemia- reperfusioninjury (I/R) in various animal and cellular models. The purpose of this application is to further demonstrate the therapeutic effect of these drugs against myocardial infarction (MI)-induced heart failure and to develop innovative approaches for long lasting protection. We will test the following hypotheses: 1) Suppression of PDE- 5A with novel class of inhibitors or targeted gene silencing with lentiviral vector in vivo reduce post MI-induced heart failure and attenuate contractile dysfunction via inhibition of cardiomyocyte apoptosis in the heart. 2). Chronic PDE-5A inhibition suppresses oxidative/nitrosative stress by increasing the bioavailability of NO, cause inhibition of NADPH oxidase/xanthine oxidase activity, inhibit activation of redox-sensitive transcription factor, NF- thereby suppressing gene expression of proinflammatory cytokines following MI induced heart failure. 3) In vivo gene transfer of cGMP dependent protein kinases (PKGs) attenuate post MI-induced remodeling and heart failure. These studies will be the first ones to demonstrate the protective effect of PDE-5A inhibitors and novel lentiviral gene silencing approaches and associated signaling pathways in post MI-induced heart failure. We anticipate that results from these investigations will provide novel insights into expanding the utility of the PDE-5A inhibitors for other cardiovascular indications in addition to their current clinical use for treatment of erectile dysfunction and pulmonary hypertension. LAY NARRATIVE Acute myocardial infarction (AMI) continues to be a major cause of morbidity and mortality worldwide. AMI is caused by a sudden obstruction to the flow in a coronary artery branch leading to myocardial ischemia (lack of oxygen) and tissue death. The long-term complication of AMI is the late occurrence of left ventricular dysfunction (`weakening of the heart') and heart failure. In this proposal, we will study the effect of erectile dysfunction drugs (Viagra, Levitra and Cialis) and novel gene silencing approaches to limit the damage of the heart following AMI. We believe that knowledge derived from these studies will provide additional tools to the cardiologists for treatment of heart failure with clinically approved erectile dysfunction drugs. In addition, our investigations will open up another innovative gene silencing option to treat AMI and ventricular remodeling in patients.